NRC chief promises thorough probe at San Onofre

Plant to stay offline until cause of tube wear determined

Under normal conditions, the plant provides about 20 percent of the region’s power. But state energy officials have warned of rotating blackouts if a heat wave hits while the units are offline.

The San Diego area faces the greatest prospects for rolling blackouts without San Onofre’s crucial high-voltage support along coastal transmission lines that sustain electricity imports from the north.

John Geesman, an attorney for the Alliance for Nuclear Responsibility of San Luis Obispo, said time is running out for a restart before summer.

“If (Jaczko) can’t make a positive indication ... if he just ducks and is ambiguous, I think that’s a pretty clear signal that there’s a problem coming up this summer,” said Geesman, who previously served on the California Energy Commission.

Pressed repeatedly on when the reactors might come back online, Jaczko said the nuclear commission was “prepared to review information (from Edison) in a timely way.”

Southern California Edison has identified two causes of the unusual wear on tubes within Unit 3. Tubes rubbing against each other and against support structures. But the reason for the tube degradation still is not fully understood.

“Definitely, Unit 3 degradation is a different type of phenomenon than we have seen with steam generators,” Jaczko said.

Generators at San Onofre were replaced between late 2009 and early 2011 at a cost of $670 million, which utility ratepayers continue to pay for.

Jaczko said Unit 2 could be restarted earlier than Unit 3 — provided that problems at both reactors are thoroughly understood.

“It is possible that they could move forward on a different path for restart,” he said. "A lot of that will depend ultimately on what the causes are. As part of their commitments to us we have asked them to demonstrate that they understand the causes of the Unit 3 degradation before they move forward with Unit 2."

No other plant shares the same generator design and manufacturer as San Onofre, Jaczko said in response to a question about implications for the U.S. nuclear industry.

As part of its probe, Jaczko said the NRC would review whether the company made any unauthorized changes to the generators. The agency has said previously it was aware of alterations.

More than 300 tubes at the two reactors have been plugged as the result of pressure testing, electromagnetic scans and other inspections. The number of retired tubes is well within operating margins that anticipate gradual degradation and corrosion, according to Edison.

The leak at the Unit 3 coincided with a small release of radioactivity into the atmosphere, which did not endanger plant workers or neighbors of the facility, according to regulators.